You can probably base a big Shuttle disaster alt-history on this
http://space.co.uk/Features/Newslet...htsoftheDeathStarPage1/tabid/628/Default.aspx
A Shuttle with a Centaur in the payload bay.
Just supose that Thiokol Roger Boisjoly managed to postpone Challenger launch to a warmer day.
You save the crew, but wreck further NASA launch schedule. In may come the Centaurs launches; in July, Vandenberg AFB pad go into service, with the hill surrounding the pad reflecting noise of the boosters at launch.
Now the Shuttle is due to imminent disaster, particularly since it carry the Centaur.
Some ways of turning a Shuttle-centaur launch into a real disaster
- Challenger again. Boisjoly feared an explosion on the pad...
January 27 1987. Twenty years after Apollo 1.
Another Shuttle is on the pad, on a morning as cold as January 28 1986, or January 24 1985 (when Discovery barely escaped disaster, leading Thiokol toward O-ring erosion problems).
Same scenario as Challenger OTL, with two main differences
- A Centaur on the payload bay
- the Shuttle explodes on the pad.
Quite paradoxically crew has better chance to survive to a blast on the pad.
But LC-39 is totally destroyed...
Other scenario : OMS pods or APU catch fire at landing and trigger explosion of LH2 boilf-off from the Centaur.